Bifocal lens



May 15, 1934.

H. A. TOULMIN, JR

BIFOCAL LENS Filed July 6, 1931 2 Sheets-Sheet, 2

INVENTOR HARRY A. TOULMl/V JR.

qZWLM' 7-M ATTORNEY Patented May 15, 1 934 BIFOCAL LEN S Harry A. Toulmin, Jr., Dayton, Ohio, assignor,

to The Univis Corporation, Dayton, Ohio, a corporation of Delaware Application July 6, 1931, Serial No. 548,757

4 Claims. (Cl. 88-54) My invention relates to bifocal eyeglass lenses ing the arrangement of the insert prior to surand the method of manufacturing. face grinding which results from the blank It is the object of my invention to provide shown in Figure 11. a very cheap and accurate method of manufac- Figure 13 is a section through the finished I turing a bifocal eyeglass lens and of providing bifocal eyeglass lens resulting from the grinding a resulting lens that requires the minimum of of the blank in Figure 12. skill in its production, as well as materials of I Referring to the drawings in detail, I provide simple form and of relatively cheap nature. rectangular strips or blocks of crown glass 1, It is a further object to provide a bifocal lens 2 and 3. I lay between the surface '4 of the having a near vision fused insert with a maxlblock 1 and the surface 5 of the block 2 a bar 65 mum breadth of the insert and produced by a or strip 6 of flint glass or of barium crown glass. method which eliminates all grinding of the The upper and lower surfaces 7 and 8 of this major lens. bar of glass 6 are roughened to form a grey It is a further object to provide ,a bifocal lens edge. This roughening may be imparted by of the cut-through type, that is, the type with chemical action, by mechanical action, or by the insert extending completely through the sand blasting. 'Its purpose is to prevent the remajor lens, which can be cheaply and efficiently flection of light in the resulting lens. I also manufactured and eliminates the difficulties may, but it is not essential, roughen the adjawhich heretofore have eidsted in manufacturing cent faces 4 and 5 of the crown glass members a lens in which the major lens had to be pierced 1 and 2 where they engage the grey surfaces 75 in order to insert the near vision portion, with 7 and 8 of the bar'6. the consequent difliculties of fusing, particularly I place the bar 3 in engagement at the back the near vision insert within the distance porof the flint bar 6 and between the surfaces 4 tion of the lens, when using glasses of different and 5 of the crown glass blocks 1 and 2. melting points and of different indices of refrac- The composite structure is then fused with the 80 tion. 1 result shown in Figure 2 so that the back 9 Referring to the drawings, Figure 1' is a perand the top edges 7 and 8 of the bar 6 are fused spective of the assembled, 'unfused raw stock to the blocks 1, 2 and 3. The block thus fused blank. Y is then trimmed as in Figure 3 to the desired Figure 2 is a similar view after fusing. outline of the lens and the trimmed block is Figure 3 is a plan view after the fused raw ground to form a rough blank as shown in Figstock blank has been cut to marginal form and ure 4. The finished lens is shown in Figure 8.

ground to shape. The inter-face 9 is illustrated as flat, but it will Figure 4 is a section on the line 4-4 of Figbe obvious to those skilled in the art that this 35 ure 3. inter-face may be given various curvatures to 90 Figure 5 is a view similar to Figure2 except produce a variety of reading additions. that it shows the arrangement of a blank for In'Flgures 5 and 6 are shown the raw stock making a cut-through type of lens. bar and. the section of the finished blank where Figure 6 is a section through such a lens as a cut-through lens is desired. Heretofore, to

40 flnally manufactured, such section being taken make a cut-through lens, it. has been the prac- 95 on the line similar to that of Figure 4. tice to take the major-lens of the distance por- Figure 7 is a perspective of the insert for the tion of the crown glass, bore a hole through the near v ision portion, such'as of flint or barium glass and then plug. the hole with a piece of crown glass showing the greyed edge. I flint glass. Then the lens blank was fused. Figure 8 is a section through the finished bi- The difficulties of making such a lens have been 1 focal eyeglass lens, the blank for which is shown numerous, amongst them being the {diiiiculty of in Figure 4. grinding the hole accurately, thedifllculty of- Figure 9 is a perspective of a blank having grinding the margin of the insert'to fit the hole, alternate inserts of flint and crown glass. and the'difljiculty of fusing due to the diiference Figure 10 is a plan view of the lens resulting in diameter of the segment and the diameter of 105 from the blank shown in Figure 9. the hole necessary for the insertion of the in- Figure 11 is a perspective of a blank in which sert in the hole. .an arcuate back insert that can be rocked to Furthermore, the adjacent edges of the insert its desired position may be employed. and the hole could not lie-roughened to furnish Figure 12 is a section similar to Figure 4 showa'grey surface toprevent light reflecti'on'because' '110 2-1 this roughening would upset the accuracy of the fit.

-By the present arrangement, relatively unskilled labor can be employed and maximum.

I place, by varying the depth of the bar 6, any

depth of reading segment may be employed. As the bar 6 runs completely across the. lens,jthe maximum width of reading field is secured. If desired, the bar 2 maybe of sufflcient depth to permit of seeing at a distance beneath the bar 6. By adequate grinding, the optical center-of the insert can be adjusted to the needs of the wearer.

Referring to Figure 9, it will be observed that if it is desired to see at a distance on either' side of the block 6, that by using 'the' crown insert blocks 10 this result may be secured. The resulting lens is shown in Figure 10. The advantage of such a lens in Figure 10 is that the optical displacement when the eye passes laterally from the reading insert to the distance portion of the lens on either side of the insert, or vice versa is greatly reduced.

Referring to the form shown in Figures 11, 12 and 13-, it will be noted that if desired this builtiup lens may'be so arranged that the optical center of the insert can-be thrown either up or down as desired. By utilizing the insert of flint glass designated 11 having an arcuate back 12 resting in the arcuate face crown block 13, having a corresponding arcuate face 14 receiving the face 12 of the insert 11, it is possible to rockthe insert 11in any angular position and fuse it in that position with the result shown in Figures .12 and 13. As shown in Figure 13- the optical center has been placed in the smaller part of -the insert, as distinguished from the upper part of the insert.

Thus by this systemof building a' lens, with strips or bars of glass having plane flat'surfaces or' simple cylindrical surfaces, quantity production of very accurate lenses can bev secured and raw stock from which lenses are made can be produced with continuous production methods,

thus materially reducing the cost without sacrificing accuracy and with an .improvement'in the reading qualities of the lenses.

It will be understood that I desire to comprehend within my invention the use of any type of glass and that when I use the term crown glass or flint glass I do not intend to be confined to this particular type of glass but employ these terms to diflerentiate concisely the glasses of different refractive indices employed. Furthermore, it will be understood that instead of building up the rough blank as in Figures 1 and 2, I may select a plate of crown glass and mill a rectangular slot in the face thereof for the reception of the flint glass insert, although I prefer a built up method'as a quicker and cheaper method, requiring no expert grinding. Likewise a transverse cut-away depression may be formed in the face of the crown glass plate having an arcuate bottom for the reception of the rocking flint insert shown in Figures 11, 12 and 13. v

Having thus fully described my invention, what'I claim as new and desire to secure by Letters Patent, is:

l. A bifocal lens of two united glass pieces only, comprising a distance lens of crown glass, and a transversely arranged insert of flint glass having a flat top and bottom and extending entirely across the distance len's from side to side thereof.

2. A bifocal lens of two' united glass pieces only, comprising a distance lens of crown glass having a transversely arranged groove therein with flat top and bottom walls and a flint. bar inserted therein extending completely across the face of the distance lens; said flint insert barbeing surrounded by the distance lens on the top, bottom and back thereof.

3. A bifocal lens blank of two united glass pieces only, compris'inga block of crown glass having a rectangular -slot extending entirely across one face thereof and an insert of flint glass fused in said slot, the upper and lower walls of said slot being flat and parallel to each other.

4.A bifocal eyeglass lens blank of united pieces of glass comprising a plate of crown glass having a rectangular slot extending entirely across one face thereof and a filler secured in said slot comprising alternate sections of crown and flint glass the flint segment thus formed having a ridge of variable height completely around its periphery.

HARRY A. TOULMIN, JR. 

